<!DOCTYPE html>
<html>

<head>
<script type="text/javascript">
    let my_window;

    function open_modal() {
        my_window = window.open('about:blank', 'window', 'modal');
    }

    function open_normal() {
        my_window = window.open('about:blank', 'my_window');
    }

    function open_invalid() {
        window.open('', 'my_window');
    }

    function close_normal() {
        my_window.close();
        console.log("window closed");
    }

    function close_twice() {
        my_window.close();
        my_window.close();
        console.log("window closed");
    }
</script>
</head>

<body>

<button onclick="open_normal()" id="open-normal">normal</button>
<button onclick="open_modal()" id="open-modal">modal</button>
<button onclick="open_invalid()" id="open-invalid">invalid/no URL</button>
<button onclick="close_normal()" id="close-normal">close</button>
<button onclick="close_twice()" id="close-twice">close twice (issue 906)</button>

</body>
</html>
